There have been proposed, as a variable magnification optical system suitable for an interchangeable lens for cameras, a digital still camera, a video camera or the like, many variable magnification optical systems which comprise a most object side lens group having positive refractive power. In these variable magnification optical systems, the has been proposed an optical system capable of focusing from an infinite distance object to a near distance obi act for moving a part of lens groups along an optical axis (for example, see Japanese Patent application Laid-Open. No. 2010-19959).